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A193109 Least k such that 2^x + k produces primes for x=1..n and composite for x=n+1. 0
0, 1, 9, 3, 225, 15, 65835, 1605, 19425, 2397347205, 153535525935 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

All terms except the first four are congruent to 15 mod 30.

a(10) was found in 2005 by T. D. Noe and a(11) was found in the same year by Don Reble.

Other known values: a(13)=29503289812425.

LINKS

Table of n, a(n) for n=1..11.

MATHEMATICA

Table[k = 0; While[i = 1; While[i <= n && PrimeQ[2^i + k], i++]; i <= n || PrimeQ[2^i + k], k++]; k, {n, 9}] (* T. D. Noe, Jul 21 2011 *)

CROSSREFS

Another version of A110096.

Cf. A092506, A057733, A104070, A144487, A008597.

Sequence in context: A248311 A038293 A119516 * A242069 A197828 A116393

Adjacent sequences:  A193106 A193107 A193108 * A193110 A193111 A193112

KEYWORD

more,nonn

AUTHOR

Arkadiusz Wesolowski, Jul 21 2011

STATUS

approved

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Last modified October 23 05:26 EDT 2014. Contains 248411 sequences.